Naturally the answer would depend on the exact photocopier and printer the questioner has. In my office's case they are the same machine so it would make no difference at all.

I know it is not what you have asked, but I must say - the best way is to cut on the papers all together. I stopped printing many things, I send copies by mail and don't use fax anymore, I put things on my cell phone and laptop, from excel sheets to books I like reading, I use backup hard drives... things like that. It saves papers and toners and I need less space in my office cabinets, it is cheaper and it is faster to make changes.

Generally speaking, the laser printer should be more efficient.

Modern photocopiers are digital - they're essentially a combined scanner and laser printer. When they're copying, they're not only using the same energy that a typical laser printer would use, but also using a certain amount of power on to scan the document. (Lights, motors, converting to a digital format.)

If you're printing by laser printer, you save on the scanning process. There is some extra power use by the computer (especially if the document is collated, so that the computer must send 100 documents to the printer, rather than one document with an instruciton to print it 100 times). But this should use less juice than the mechanical processes that drive the photocopier's scanner.

But most of the power consumption by these devices is used in standby mode. If you want something that prints the moment you hit a button (common with photocopiers), it probably means that the device is using up a significant amount of power while idle keeping coils hot so it doesn't have to warm up. Technology is improving, though, and some newer devices combine low energy consumption while idling with a fairly rapid warmup.

Regarding the suggestion to avoid printing altogether - this saves on power spent in printing the document, but, of course, it means that people must use power to read it. In many cases, this probably leads to a net saving.

You can create an even bigger saving by not creating the document in the first place - although I doubt it's a solution most offices would relish.

I made a suggestion on cutting down on papers just becouse when thinking of environmentally friendly at office people tend to think of cutting down energy consumption. But it is not all there is to it! ;-)